Abstract
This work evaluated the qualitative and quantitative cellular changes induced by treatment with 5-aminouracil (5-AU) and a combination of 5-AU and caffeine in plant cells in relation to DNA damage, repaired damage, and residual damage. As biological material, Allium cepa L. root tips were used, grown in filtered water, in darkness, with aeration at constant temperature of 25 degrees C +/- 0.5. Cell populations were synchronized using 5 mM caffeine in order to study the effects of 5-AU and caffeine/5-AU combined treatment on the DNA content and their incidence in the entrance to mitosis. The results showed a delay in the G2 period due to induced DNA damage by the 5-AU and caffeine/5-AU combined treatment, shown by aberrant metaphases, anaphases and telophases. The effect of caffeine in the combined treatment was heightened in spite of lengthening the checkpoints route that retains the cells in G2. The existence of G2 checkpoints was shown in the cell population studied, inducing lesions in the DNA, chromosomic aberrations and cellular instability.
Highlights
Proteins responsible for the regulation of the cellular division cycle are under strict control of systems that trigger or block the machinery of the cycle in the correct order and once per cycle, responding to intra - and extra- cellular information which assure that the cycle is perfectly developed (Forrest et al, 2001; McGowan, 2002; Park and Lee, 2003).When these control systems receive an inhibitory sign as the one caused by an incomplete process, the cycle is blocked by some elements of transition called negative regulators or checkpoints (Rao and Johnson, 1974; Nurse, 1994)
There are three important checkpoints during the cell cycle: the first one located in G1/S, where the entrance to replication is blocked because of unfavorable environmental conditions or inappropriate cellular growth; the second one located in the entrance to mitosis, (G2/M), where the cycle is blocked if the replication of the DNA has not been completed or there is damaged DNA; and the third checkpoint (M/G ) activated during the change of metaphase to anaphase, when the chromosomes have not joined to the microtubules of the mitotic spindle or it has not been formed correctly (Harwell and Weinert, 1989; Murray, 1992)
This effect is shown as heterophasic bimitosis, indicating that the negative G
Summary
Proteins responsible for the regulation of the cellular division cycle are under strict control of systems that trigger or block the machinery of the cycle in the correct order and once per cycle, responding to intra - and extra- cellular information which assure that the cycle is perfectly developed (Forrest et al, 2001; McGowan, 2002; Park and Lee, 2003) When these control systems receive an inhibitory sign as the one caused by an incomplete process, the cycle is blocked by some elements of transition called negative regulators or checkpoints (Rao and Johnson, 1974; Nurse, 1994). The positive mechanisms of regulation are better known than the negative ones; their implications in the regulation in normal and altered cells are similar in both cases (Park and Lee, 2003)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
